APOD 4.1

Millions of Stars in Omega Centauri
http://apod.nasa.gov/apod/ap100331.html

This is a picture of the globular cluster Omega Centauri, also known as NGC 5139. It was discovered by Edmund Halley in 1677, who did not at the time realize what it was. John William Herschel recognized it as a globular cluster in the 1830s. It contains around 10 million stars and is about 12 billion years old. It orbits the center of the Milky Way in the halo of the galaxy; it is the largest and brightest known globular cluster to do so. Because it is different from most other globular clusters, it is thought to have a different origin; it is speculated that it is the remnant of the core of a dwarf galaxy that was incorporated into the Milky Way.